SINGAPORE: Did Leslie Khoo Kwee Hock, who allegedly killed his lover, suffer from a mental condition called Intermittent Explosive Disorder as diagnosed by a private psychiatrist?
The question was at the heart of Khoo’s trial on Tuesday (Mar 26), with the prosecution seeking to debunk the diagnosis made by Dr Ken Ung.
Khoo, 50, is accused of killing Chinese national Cui Yajie at Gardens by the Bay in 2016.
Deputy public prosecutor Tan Wen Hsien interrogated Dr Ung in court over four hours about his report on Khoo's disorder, which is central to the accused's defence.
Khoo's lawyers have been relying on it to prove diminished responsibility, which could relieve him of the murder charge.
The private psychiatrist's diagnosis is contrary to that of Dr Kenneth Koh from the Institute of Mental Health.
The High Court heard on Tuesday that in writing his report, Dr Ung had interviewed only Khoo, whom he was aware had lied in his statements to the police, as well as Khoo's wife Madam Toh Lee Nah, who had expressed hope that what she said would help her husband.
One of Ms Tan's questions was in relation to a criterion for the diagnosis, which requires aggressive behaviour to be "grossly disproportionate" to the magnitude of psychosocial stressors.
Ms Tan asked how Dr Ung measured Khoo's behaviour based on three incidents assessed in his diagnosis - when Khoo caused a hole in the partition wall and broke a pen at work, and the murder.
She asserted that Dr Ung did not have enough context such as the content of the conversations that led to the incidents at work.
In response, Dr Ung said that while there was no “precise context” other than for the murder, the other incidents can be taken as part of a day-to-day work context.
That is the context that is relevant, he said, because “if we rely on minutiae, the problem is that the memory is prone to errors”.
Ms Tan also questioned Dr Ung on another criterion, which requires verbal or physical aggression, not leading to destruction of property or physical injury, to be exhibited twice a week over at least three months.
Dr Ung said that he based this on his interviews with Madam Toh, whom he spoke to once over the phone for about 20 minutes and later sent an email questionnaire to.
“She said prior to 2012, 2013, (this would happen) a few times a week,” he said.
Khoo would have qualified for a diagnosis of the condition at some point, Dr Ung added.
The prosecution also sought to prove that his condition had not manifested at the time of the murder.
Dr Ung was asked if it is necessary that every outburst from someone suffering from Intermittent Explosive Disorder be due to their condition. The psychiatrist said it is not, as the condition can sometimes be in remission.
Judicial commissioner Audrey Lim asked him again: “You would not know for a fact that Intermittent Explosive Disorder would be operating on the accused at the time of offence?”
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Dr Ung concurred, saying it is based on probability. In someone with the mental condition, he would expect to see a pattern of verbal or physical outbursts, or both, he added.
Dr Ung also said in court that Khoo had witnessed violence as a child. He saw his mother chasing his father with a chopper and had himself been threatened with one. He was also beaten by both his parents, said the psychiatrist.
However, when asked if he verified this information with any other sources, Dr Ung said he did not.
The trial resumes on Wednesday, with an inspection of the car driven by Khoo on the day of the murder and the testimony of rebuttal witnesses.
If convicted of murder, Khoo may be given the death penalty.